Optical apparatus.



No. 635,027. Patented 0ct l7, $99.;

W. SCANTLEBURY.

OPTICAL APPARATUS.

(Application filed Oct. 18, 1,898.)

(No Model.)

INVENTOR 1N: nouns PIZYERS co mm'muma. WASHINGTON, u c.

Ihvtrn STATES PATENT prion.

\VILLIAM SOANTLEBURY, OF ANACOSTIA, DIS'IRICTOF COLUMBIA.

OPTICAL APPARATUS.

SPECIFICATION forming part of Letters Patent 0.535027, dated October17', 1899.

Application filed October 18,1898. Serial No. 693,865. No model.)

To ctZZ wltont (It muycoltccrlt:

Be it known that I, WILLIAM SOANTLEBURY, a citizen of the United States,residing at Anacostia, in the District of Columbia, have inventedcertain new and useful Improvements in Optical Apparatus; and I dohereby declare the following to be afull, clear, and exact descriptionof the invention,'such as will enable others skilled in the art to whichit appertains to make and use the same.

This invention relates to apparatus for illustrating certain phenomenain the properties of rays of light and their action on the hum an eye;and it consists in the novel construction andcombination ofthe partshereinafterfully described and claimed.

In the drawings, Figure 1 is a plan view of the apparatus. Fig. 2 is aside view of the same. Fig. 3 is a cross-section taken on the line 00 a;in Fig. 1. Fig. 4 is a detail view of the shutter.

A is a supporting frame or stand.

13 is the object to be exhibited, in this case consisting for thepurpose of illustration of a disk provided witha white or colorlessbackground and having black radial bars I) upon it. The background maybe transparent and the bars may be opaque; but the object to beexhibited may be varied indefinitely in form, color, and material,provided it bears some visible mark, markings, or device uponits surfacewhichis in contrast to its background.

The object or disk Bis set in motion, so that The shaft 0 is providedwith a crank-handle D for revolving it. Any other approved drivingmechanism may be used to keep the ob- ;ject l3 in motion, such as anelectric motor.

E is a lamp or lanthorn for illuminating the object 13. The apparatus isused in the dark, and any approved means for casting a beam of light onthe object maybe used, such as the said lamp. When the object B isopaque, it is preferably arranged at a considerable distance from thelamp, so that it can be seen byseveral persons. When the object istransparent or partiallytransparent, a screen If. may be placed behindit, and the object may then be placed closer to the lamp, as the pictureof it on the screen can be studied by a number of persons, and thechanges in the picture on the screen are in many respects the same asthose seen when looking at the object itself.

F is a shutter interposed ,betw'eenthe lamp and the object B or itspicture on the screen. This shutter preferably consistsof a perforateddisk, and several perforations f are preferably used. The disk F ismounted on a shaftf, carried by the frame, and. it is re volved rapidlyby any approved means. One perforation fwould be operative; but a series of perforations f is preferably provided in the disk in order thatit may not have to be revolved atso high a speed as it would if only oneperforation were provided.

The means for revolving the disk F preferably consists of a small pulleyG, secured to the disk, a large pulley g, mounted on a shaft g, which isjournaled in the frame, a

crank-handle G, projecting from the pulley g, and a cord 3', passingaround the pulleys G and g. Y

In operating this apparatus the shutter is revolved at a much greaterspeed than the object under observation. Then the object is stationaryand the shutter is revolved rapidly, the beams of light from the lampilluminateit by passing through the perforations of openings fin rapidsuccession, and the object or its picture on the screen is almost asclearly visible as if the shutter were stationary and the lamp projectedan unbroken beam of light through one of its perforations continuously.The dotted lines at indicate the light proceeding from the lamp, the object B being arrangedvfholly within the field of illumination. When theshutter is stationary and the illuminated object isrevolved rapidly, thedevice on it becomes invisi l le. The radial black bars of the diskshown in the drawings become blurred and merged into the Whitebackground, so that a very pale gray disk is seen. When the shut ter isrevolved rapidly and the hand and arm are waived in front of it, or thedisk is revolved at a moderate speed corresponding with that of waivinga hand and arm and so that the device on the disk is not whollyinvisible, the usual phenomena resulting from the persistence of visionand as heretofore demonstrated by the stroboscope are observable. 'When,however, both the disk B and the shutter are revolved with the rapidityhereinbefore described, some very peculiar phenomena are observable.Numerous radial black lines now appear visible on the normally-invisibledisk B, with white spaces between them. The number of these black linesvaries greatly, according to the ratio or difference of the speeds ofthe disk I; and the shutter. With a certain change in the ratio of thespeed of the shutter with relation to the speed of the (llsk B whiteradial lines appear having dark-gray spaces between them. The number ofthe black or white lines is in excess of the number of bars actually onthe disk, and althougl'l at some ratioof the speeds these lines appearstationary they usually have a circular motion, sometimes revolvingslowly in the direction in which the disk is actually turning andsometimes revolving slowly in the reverse direction. \Vithin certainlimits of speed a very small change in the rat-i0 of the speeds of thedisk and shutter makes a great difference in the appearance of what isseen on the disk.

This apparatus is used in the lecture-hall to demonstrate and exhibit tostudents the phenomena hereinbefore described for the purpose ofillustration, and also many other The wheel It bears against the side ofthe pulley C, which forms a friction-disk. The shaft H is connected tothe shaft g by intergeariug beveled toothed wheels h. The friction-wheelh is provided with a suitable haudle 2', which engages with a groove inits hub and affords 'a means for sliding it on its shaft, and its shaftis graduated to indicate the difference in the ratio of the speeds ofthe disk B and the shutter. Both shutter and disk can be revolved byturning the crank-handle G, or the friction-wheel h can be slid out ofcontact with the pulley O, and the pulley C can be revolved separately.

What I claim is 1. In a stroboscope, the combination, with a source oflight, and an object arranged wholly within the field of illumination;of a shutter arranged between the said sou roe of light and object, anda single driving device and intermediate connectionsoperatingto revolvethe said object and shutter simultaneously, substantially as set forth.

2. In a stroboscope, the combination, with a source of light, and anobject arranged wholly within the field of illumination; of a shutterarranged between the said source of light and object, a single drivingdevice and intermediate connections operati ngtorevolve the said objectand shutter simultaneously, and means for varying the ratio of thevelocities of the said object and shutter, substantially as set fort-h.

3. In a stroboscope, the combination, with a source of light, and anobject arranged wholly'within the field of illumination; of a shutterarranged between the said source of light and object, a single driving.device 0perat-ing to revolve the said object and sh uttersimultaneously,andintermediateconnections provided with a slidablefriction-wheel permitting the ratio of the velocities of the said objectand shutter to be varied while the said parts are in motion,substantially as set forth.

In testimony whereof I affix my signature in presence of two witnesses.

WILLIAM SOANTLEBURY. Witnesses:

HERBERT W. T. J ENNER, BERTHA L. DANA.

